Arcograph.



A. W. ALLEN.

ARCOGRAPH.

APPucmou man un. 21. |914.

1,146,607. Patented July 13, 1915.

.JLUMBIA PLANCKIIAFN couWAlilNfoN. D. C.

D STATES PATENT onirica.

ALONZO W. ALLEN, OF STREATOR, ILLINOIS, ASSIGNOR OF ONE-HALF TO EMANUEL M. DAVIS, OF STREATOB, ILLINOIS.

ARCOGBAPH.

Bpeoiiication of Letten Patent.

Patented July 13, 191.5.

T0 all 'who-m 'it may concern Be it known tiat I, ALoivzo W. ALLEN, citizen oi the United States, rcsidin at 'ritrcator, in the county of La Salle and btate of Illinois, have invented new and useful Improvements in Arcograplis, of which the following is a specification.

My present invention pertains to arcogra}.)hs,'aml is designed more particularly as an improvement on the arcograph con-v stituting the subject of my Letters-Patent Number 915,920, dated March 23, 1 909.-

The object of the present invention is to provide an arcograph having such capacity that its arms are adapted to swing or turn both ways from a straight line, this with a view to using the device for the drawing of reverse curves without the necessity of changing the position of the instrument: In other words curves can be drawn in either direction close to a wall provided the table is fastened to a side wall.

A secondary object of the invention is the provision of an arcograph with which may be used any pencil or drawing pen thereby doing away with the necessity o an appliance for holding a pen or pencil as in my before mentioned Letters-Patent.

The invention further contemplates the provision of an areograph in which the guides can be adjusted in such manner as to avoid marring of the table this being feasible inasmuch as the weight of the instrument tends to assist in holding the same in position.

Another advantageous feature of the in vention is the construction which permits of the arcograph being folded into small compass.

With the fore oing in mind the invention will be fully un erstood from the following description and claims when the same are read in connection with the drawings, accompanying and forming part of this specilication, in which:

Figure l is a plan view illustrating the three members o my novel instrument as the same appear when properly arranged in the first instance relative to a cord line from which the arc of a circle is to be drawn. Fig. 2 is a detail section illustrative of the manner in which the arms are connected together and to the main stem. Fig. 3 is an enlarged section illustrative of the slidable member on the main stem. Fig. l is a transverse section taken through one of the arms and showing the manner in which the index devices are mounted on the arms. Fig. 5 is an enlarged plan of one of the auxiliary members. Fig. 6 is a lon itudinal section oi" one of the auxiliary mem ers or guides.

Similar numcra s of reference designate corresponding parts in all of the views olf the drawings.

Among other elements my improved device comprises a. main stem l. This stem is provided with a graduated scale, and the said scale is numbered as shown in Fig. l. At one end the scale is notched as indicated by 2 so as to form a guide for the pencil or pen used in connection with the device.

Connected to the stem 1 and to each other in the manner shown in Fig. 9. are two arms 3. As will be readily observed theI said connecticn is such that the arms may be expedi tiously and easily adjustably fixed relative to each other and the stem 1: the connection comprising a threaded pintle 4 and a binding nut 5. On each of the arms 3 is a rail (i, of dove-tail form in cross-section, and on the said rail is mounted an index device 7, equipped with a set screw 8.

Mounted to slide on the main stem 1 is a body 9, equipped with a set screw 10. The said body is rovided with lateral projections 11, and pivotally connected to these projections and also to the arms 3 are bars 12.

13-13 are the auxiliary members or uides of the device. These auxiliary memers or guides are identical in construction and therefore a detail description of the one shown in Figs. 5 and 6 will sufliee to impart a definite understanding of both. As will be readily manifest the member referred to is iprovided at 14 with a screw threaded pointed pin by which it may be adjustably xed in position. The adjustable capacity of the said in is advantageous inasmuch as it enables t e )in to be set in such position as not to mar t ie board on which the device is used.

By using my novel instrument or device compound curves such as used in laying out railways, can be readily drawn and nicely com ounded, the mode of procedure being as fo lows: It will be understood that when the apex of the angle is at the point of either auxiliary member or guide 13 that a line drawn with the arm is a tangent to the curve, and at right angles with the tangent lOll is a radial line. By extending the tangent to the left of the point and placing the left hand arm on this tangent and setting the angle so that the right hand arm will come to any point, the curves will compound. .y

The indexes 7 are used to determinethe positions of the guide members 13. This will be understood when it is stated that when the radius and de ree of the are to be drawn are known, the Iength of the chord may be determined and the indexes set equidistantly from the bar 1 at a distance apart equal to the length of such chord and serve to indicate the proper positions of the members 13 in using the device.

Having described my invention, what I claim and desire to secure by Letters-Patent, is:

1. A device for the purpose described, comprising a stem, arms pivotally connected together and' to the stem, means whereby said arms can be accurately fixed in predetermined mathematicall -correct ositions relative to the stem, an indexes a justable on the arms in the direction of the length thereof.

2. A device for the purpose described comprising a stem, arms pivotally connecte together and to the stem, said arms having rails of dove-tail form in cross-section, indexes ad'ustable on said rails, and means for adjustably lixinn' the indexes to the rails.

3. In means or the the combination of auxiliary members or guides provided with means for holdin them in position on a drawing surface, and a major member having arms capable of swinging in both directions from a straight Copies of this patent may be obtained for purpose described,

line'and adapted to be set against said auxiliary members or guides and also having indexes adjustable on the arms in the direction of the length thereof.

4. In means for the purpose described, the

ycombination with auxiliary members or guldes having points and also havmff means for holdin them in position on a rawmg surface, o a major member comprising a stem having a notch in its forward end, arms pivotally connected together and to said stem at a point adjacent to the notched end of the stem, and means for adjustably fixing the arms relative to each other and the stem.

5. In means for the purpose described, the combination with auxiliary members or guides having points and also having means for holdin them in position on a drawing surface, o a major member comprising a stem having a notch in its forward end and arms pivotally connected together and to said stem at a common point adjacent to the notched end of the stem.

6. A device for the purpose described comprising a stem having a notch iu its forward end, arms pivotally connected together and to said stem at a common point adjacent to and in rear of the notched end of the stem, and means for adjustably fixing the arms relative to each other and the stem.

In testimony whereof I have hereunto set my hand in presence of two subscribing wit nesses.

ALONZO W. ALLEN.

Witnesses:

EvAN D. Rosn'rs, C. 4H. Hanna-MAN.

Ave cents oaoh, 'by addressing the Commissioner of Patents.

Washington, D. 0. 

